This paper presents a model to calculate the sulphate agent amount and sulphate agent ratio for fine grounded and fast hardening Portland cement clinker. Despite sufficient knowledge about the influence of calcium sulphate on the hydration process of cement, the sulphate agent amount is mostly adjusted empirically. As a result, often a wide and unfeasible experimental matrix has to be tested. In this work, Design of Experiments (DoE) was used in combination with in-situ X-ray diffraction (XRD) tests to accurately adjust the sulphate agent of different finely ground cement by calculation. With only 42 tests, it was possible to analyse in total the influence of the sulphate agent, the grinding fineness and the use of C-S-H-seeds for the use in fast-hardening Portland cement-based systems. In addition, it was found that a hemihydrate to anhydrite content of 25/75 leads to a stabilisation of the hydrated system in the first 24 h of hydration. A model for the optimisation of the sulphate agent composition in dependency of the cement fineness could be determined. Furthermore, it was shown that the DoE also provides optimal results in material sciences in a resource-saving way.
Keywords: C-S-H-seeds; Portland cement clinker; design of experiments; fine ground clinker; sulphate optimization.